Technical data

Metadata

Technical information 

Data source: Data on macrobenthic community composition was obtained during monitoring cruises of the Finnish Institite of Marine Research since 1964-65. The data is stored in the database of of the Finnish Environment Insitute (SYKE). The contact person at SYKE is Alf Norkko.

Description of data: Data from multiple monitoring stations per open sea area over the period 1964-2007 is used. Values are presented as mean of 3-5 parallell samples (sampler area 0.1 m², sieved on 1 mm mesh size), and are multiplied to values per square meter. The data are collected within the framework of the HELCOM COMBINE programme.

Geographical coverage: All regions of the Baltic Sea except for the Gulf of Riga, the western Gotland Basin, the Danish Straits and Kattegat.

Temporal coverage: From 1964-65 to 2007.

Methodology and frequency of data collection: Sampling and analyses are made according to the guidelines for the HELCOM COMBINE programme. Sampling is performed once a year in May-June.    

Methodology of data analyses: The status of the Baltic Sea according to the described indicator has been classified using the multi-metric indicator-based HELCOM Eutrophication Assessment Tool (HEAT). Each area was assessed using information on reference conditions (RefCon) and acceptable deviation from reference condition (AcDev) combined with national monitoring data from the period 2003–2007. The basic assessment principle is RefCon ± AcDev = EutroQO, where the latter is a "eutrophication quality objective" (or target) corresponding to the boundary between good and moderate ecological status. When the actual status data (average for 2003-2007) exceeds the EutroQO or target, the areas in question is regarded as affected by eutrophication.

The Ecological Quality Ratio (EQR) is a dimensionless measure of the observed value (AcStat) of an indicator compared with the reference value (RefCon). The ratio is equal to 1.00 if actual status is better than or equal to reference conditions and approaches 0.00 as deviation from reference conditions becomes large. The value of EQR is used to assign a quality class to the observed status. The classes in descending order of quality are RefCon, High, Good, Moderate, Poor, Bad. The central definition of the quality classes is given by the value of acceptable deviation (AcDev).

The RefCons and AcDev values for the benthic invertebrate assessment were first defined by a group of national experts from the HELCOM Contracting Parties for the HELCOM thematic assessment on eutrophication (HELCOM 2009a). The first assessment was based on identifying the status for the period 2001-2006, including data from coastal areas. This assessment covers the period 2003-2007 and includes data from only open sea areas.

For a complete explanation of the methodology used, please see Andersen et al (2010) and thematic integrated assessment on eutrophication of the Baltic Sea (HELCOM 2009a).

The eutrophication status maps were produced by spatially interpolating the values for the areas listed in the data table. ArcGIS 9.3.1 was used to interpolate the open and coastal areas. The coastal areas interpolation was delimited by a 6 nautical miles buffer along the coastline. The result was then joined to the open sea areas and the final map was processed to add a smoother transition between coast and open sea areas. Due to the availabliity of data from only open sea areas, the coastal areas (up to 6 nautical miles from the coastline) are shown as white to represent the lack of data.

Strength and weaknesses of data:  Benthic invertebrate communities are good indicators of environmental status. Owing to their relative longevity (years to decades), the composition of benthic communities integrates environmental conditions over longer periods of time. Hence, variations in environmental characteristics, such as salinity, oxygen, food supply, biotic interactions, and different types of disturbances (both natural and anthropogenic), are reflected in the composition of communities in time and space.

Reliability, accuracy, robustness, uncertainty (at data level): This assessment concerns benthic invertebrate status only in open-sea areas.

Inclusion of coastal water areas in the assessment is challenged by the different indices used in different countries and the wide range of acceptable deviations made use of in the 2009 HELCOM thematic assessment on eutrophiction. There is an evident need for careful intercalibration.

Further work required (for data level and indicator level): The indicator will be updated annually, both in terms of the rapid assessment and the quantitative data. Due to the labour required for sorting macrofaunal samples, the quantitative data lags behind with one year.

References

Andersen, J.H., P. Axe, H. Backer, J. Carstensen, U. Claussen, V. Fleming-Lehtinen, M. Järvinen, H. Kaartokallio, S. Knuuttila, S. Korpinen, M. Laamanen, E. Lysiak-Pastuszak, G. Martin, F. Møhlenberg, C. Murray, G. Nausch, A. Norkko, & A. Villnäs. 2010. Getting the measure of eutrophication in the Baltic Sea: towards improved assessment principles and methods. Biogeochemistry. DOI: 10.1007/s10533-010-9508-4.

HELCOM 2009a. Eutrophication in the Baltic Sea. An integrated thematic assessment of the effects of nutrient enrichment in the Baltic Sea region. Baltic Sea Environment Proceedings No. 115B.

HELCOM 2009b. Biodiversity in the Baltic Sea. An integrated thematic assessment on biodiversity and nature conservationin the Baltic Sea. Baltic Sea Environment Proceedings No. 116B.

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Last updated: 26 May 2010